A Toxicologist Explains What You Should Know About Toxins in Food

There are juice cleanses to supposedly get rid of them, celebrity-approved products that claim to be free of them, and everywhere you go these days people seem to be talking about them. Toxins. But what are toxins really? The dude slinging $9 green juice is vague, and I'm pretty sure he isn't the one you want to rely on for health information anyway.

Instead I turned to a toxicology expert to answer some basic questions about poisonous compounds in food — and learned five essential facts about toxins in the human diet.

1. "A toxin is a compound at specific amounts that gives you an adverse effect on health."

That's the fundamental definition according to Dr. Roger A. Clemens, food safety and toxicology expert and adjunct professor of pharmaceutical sciences at the USC School of Pharmacy.

The "specific amounts" portion of the definition is important because ...

2. With toxins, the dose makes the poison.

Paracelsus, the Renaissance physician who is considered the father of toxicology, coined the above adage, which neatly expresses the idea that a toxic compound is harmless until a certain level of exposure is reached. Only at that point does the compound become harmful.

If consuming even a minute amount of a potential poison makes you leery, remember that we actually need certain toxins. Vitamin A, for example. In large doses, it is toxic, but if you were to avoid this potential toxin altogether, you would suffer from vitamin A deficiency and its accompanying health problems.

3. There is no difference between man-made and naturally occurring toxins.

In other words, the toxins that plants make are not "better" than synthetic toxins just because they are natural. Both have the potential to be either harmless or harmful. "At the end of the day, it depends on the concentration, the amount of exposure, and the recurrence of that exposure, or duration of that exposure, that really makes a difference," says Dr. Clemens.

4. Most toxins we eat are natural, not synthetic.

Here are some common fruits and vegetables which contain naturally occurring toxins:

Carrots: "Carrots contain carotatoxins and myristicin, and those are toxins, yet they're in such small doses, we clearly see the benefits versus the adverse effects."

Eggs: "Egg whites contain a factor called avidin and avidin is a biotin binder. (Biotin is a vitamin.) So if you eat raw eggs or undercooked eggs, egg whites in particular, you consume avidin and it binds biotin. And if you don't have biotin, you can't do cellular respiration. Well, that doesn't sound very good, does it? Leads to a condition called alopecia. You lose your hair!"

Potatoes: "Potatoes with green spots contain compounds that are glycoalkaloids, which are toxic."

Mushrooms: "Of the 2,400 varieties that are known, only 20 of them are edible. Most of the rest of them contain compounds that inhibit cell division."

Avocados: "Avocado skins and avocado pits contain persin. Persin is a known toxin, but we don't eat the skin, we don't eat the pits — we only eat the flesh, so it becomes a non-issue."

Apples, peaches, pears, apricots, cherries, and other pitted fruits: "These pits contain a classification of compounds called cyanogens. We know that cyanogens are lethal, yet we eat the fruit and it's not an issue."

5. Healthy foods are full of toxins — but that may be a good thing.

Did you know cabbage contains about 50 different carcinogens? Yet many studies have linked eating cabbage and related vegetables, like kale and broccoli, to a decreased risk of various types of cancer. "One could argue that compounds we find in cabbage and apples and peaches and other foods that we enjoy that protect the plant are actually beneficial for humans," says Dr. Clemens. "The toxins we find in plants, with very few exceptions — it's all about the dose — are not harmful for us."

The truth is that we eat toxic compounds every day. But once you understand the facts about toxins, that starts to sound a lot less scary than it seems.